SCToni - thanks for the morning laugh. Not a lovely picture there that you painted. Gives a different twist fo "buttface".
I was on a flight once where a few rows ahead of me a particularly buxom young lady was stepping over the guy in the aisle seat. She was facing him and he was sound asleep. We hit turbulence and she landed "pillows first" into his face. I burst out laughing. Not intentionally, it just came rolling out... At first the pax was upset, then pleased, then embarrassed. She was mortified and ran down the aisle to the Lav. I wondered how the rest of their flight went, and if they met later for a date, since the preliminaries had already been made.
I like your recommendation of talking about it prior to takeoff. That's such a simple and respectful way to handle it. Some will say step over me, some will ask to be nudged. Everyone's different.